O2S Stays at Center
O2S STAYS AT CENTERWhen Monitored
With the engine running for more than 2 minutes and engine temperature greater than 170°F.
Set Conditions
The oxygen sensor signal voltage is 0.5 volts for 1.5 minutes.
Theory of Operation
The oxygen sensor is a voltage generating device. The Powertrain Control Module (PCM) receives exhaust gas information from the O2 sensor. The sensor detects exhaust gas content by a galvanic reaction within the sensor that produces a voltage. After measuring the amount of oxygen in the exhaust gases, the oxygen sensor can tell the PCM how well its output signals are controlling the air/fuel ratio. Variations in the signals from the O2 sensor serve as air/fuel ratio indicators. Changes in the sensor signals occur because the air/fuel ratio is constantly changing. When oxygen content is low (rich mixture), the voltage signal will be approximately 1 volt. With a lean mixture (high oxygen content), the voltage signal will be low, approximately 0.1 volt.
Possible Causes
- Sensor output wire open.
- O2 sensor failure.